Geology and Natural History. 171 



but 7 are extinct, or about 5 per cent. Of animals, there are 540, 

 of which 203 are extinct. The amount of extinction is not, how- 

 ever, general to all the kinds of animals, for among the 298 forms 

 of molluscs it is but 2 per cent, while in the insects (108) it rises 

 to about 96 per cent, and among the vertebrates (130) to more 

 than 71 per cent. 



In the first interglacial time, the Aftonian, there are now 

 known 89 species. None of the invertebrates and plants is 

 extinct, while of the 25 vertebrates not less than 23, or 92 per 

 cent, are no longer living. The greatest abundance of known life 

 is in the third interglacial time, the Sangamon, having 314 

 species. 



" It is singular that the bones of Homo have not been found in 

 America in connection with interglacial deposits," that is, in "no 

 undisputed" interglacial one "in the territory once covered by 

 the great ice sheets." The author, however, appears to agree 

 with Hay that the human remains of Vero, Florida, may be of 

 early or middle Pleistocene time (pp. 373-374). 



' ' The interglacial intervals, especially the Yarmouth and San- 

 gamon intervals, were of wide extent and long duration. . . It is 

 probable that conditions during these intervals were not largely 

 different from those of to-day, at least during the temperate 

 period of the intervals. Factors of stratigraphic differentiation 

 must be found in the insects and mammals, the plants and mol- 

 lusks being of little value for this purpose on account of their 

 uniformity through the interglacial intervals. Plants, however, 

 are good indicators of climatic changes and have had, and will 

 continue to have, an especial value in placing the climate of the 

 fauna which may be found associated with them. Mollusks are 

 excellent indicators of ecological conditions, which they usually 

 rather accurately attest." (372-374.) c. s. 



II. Miscellaneous Scientific Intelligence, 



1. The Professionl Preparation of Teachers for American 

 Public Schools. — Carnegie Foundation for the Advancement of 

 Teaching. Pp. xix, 475 with 85 tables and a map of the State 

 of Missouri. New York, 1920. — This report is based upon an 

 examination of tax-supported schools in Missouri by W. S. 

 Learned, W. C. Bagley and others. It originated in an investi- 

 gation requested by the Governor in 1914, but the study of the 

 local situation has been found to involve a thorough-going exam- 

 ination of the whole teacher-training problem in the United 

 States, hence there results a wide application. Among the 

 conclusions arrived at are the following. The teacher-training 

 function of the state should be exercised by a single directing 

 body, the "normal schools" and colleges being treated together 

 as a part of the whole system of higher education. Further the 



